In the current coding, eigenvalues were accessed directly through the
data field of the related struct.  This led to many eigenvalues being
reported zero.

The correct way to access the eigenvalues is with a specialized function
(gsl_vector_complex_get()) which returns both the real and imaginary
parts.

With the present fix, the matrices stored in data/*.fits are no longer
reported to have half of their eigenvalues zero.

Fixed-by: Robin Williams